In the machine tool industry and in the field of automation wherein workpieces are supported on a gripper head for movement into a machine or tool, for disengagement of the workpiece, retraction of the gripper head with subsequent advance of the gripper head gripping the finished workpiece and the subsequent retraction of the gripper head for removing the finished workpiece from the machine tool and for transporting the workpiece to a predetermined location. Various types of power operated cylinder assemblies which have been provided with associated gripper heads having pivotal jaws and wherein a power cylinder is employed for effecting reciprocal feed movements of the jaw assembly and for effecting opening and closing movements of the jaws.